This invention relates generally to a scheme for stabilizing the operation of an adjustable speed a-c electric motor that is driven by static electric power conversion apparatus. More particularly, the invention relates to method and apparatus for stabilizing the operation of a current fed induction motor drive system, and it is also applicable to voltage fed induction motors and to drive systems employing synchronous or synchronous-reluctance motors.
The background of this invention is the same as the "Background of the Invention" set forth in the above-reference concurrently filed patent application Ser. No. 729,042, which application is incorporated herein by reference in its entirety. That application discloses an improved a-c motor stabilizing scheme comprising suitable means for deriving an angle feedback signal representative of the actual phase angle between electric current and electromagnetic flux that interact to produce torque in the motor when excited and means responsive to the angle feedback signal for controlling the power conversion apparatus so as to control the stator excitation frequency of the motor as a function of the angle feedback signal.